Big tasks, often due later, can be tackled by breaking them down into smaller pieces and scheduling dedicated time for each.
But because of the lag between assignment and delivery, you could fall into the temptation of holding the task off until later, only to find yourself cramming one day because you realize that the workload is too much for an overnight.
The best way to deal with important tasks is to commit yourself to the schedules you have set. If you don’t, you risk shipping out something that could have been better. But you will not know what could have been if you do not give yourself enough time to do the work and make it better.